php 文件下载 出现下载文件内容乱码损坏的解决方

public function download()
{
  $upload=M('upload');
  $data=$upload->find($_GET['id']);

  if(empty($data)){
    header('HTTP/1.0 404 Not Found');
    header('Location: .');
  }else{

  $path='./public/Uploads/'.$data['savename'];

  header("Content-Type:".$data['type']);

  header('Content-Disposition: attachment; filename="'.$data['name'].'"');

  header('Content-Length:'.$data['size']);

  ob_clean();
  flush();

  readfile($path);

  }
}